Gear.



H. N. ANDERSON.

GEAR.

APPLICATION FILED. AUG. 28. l9l3.

PatntedSept. 26,1916. 1

4 SHEETS-SHEET I 3 who; as Zr 1 a I l) H. N. ANDERSON.

GEAR.

APPLICATION man AUG-28,1913.

1 1 99, Patented Sept. 26, 1916.

4 SHEETSSHEET 2.

H. N. ANDERSON.

GEAR.

APPLICATION FILED AUG-28,1913- v 1 1 99, 332 Patented Sept. 26, 1916.

4 SHEETS-SHEET 4' another object is to provide a simple and y UNITED STATES PATENT OFFICE.

HAROLD N. AI Q'DERSON, OF CLEVELAND, OHIO, ASSIGNOR TO THE ANDERSON ROLLED GEAR COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

GEAR.

Specification of Letters Patent.

Application filed August 28, 1913. Serial No. 787,215.

To all whom it may concern- Beit known that I, HAROLD N. ANDERSON, a. citizen of the United States, residing'at Cleveland, county of Cuyahoga, and State of Ohio, have invented certain new and useful Improvements in Gears, of which the following is a full, clear, and exact description.

This invention, which constitutes the subject matter of this application, relates to rolled toothed objects, such as gear wheels, racks and the like, and the process of manufacture thereof.

One object of my invention is to provide such articles with gear teeth which shall be stronger, more accurate and more durable than have been heretofore produced, and

economical process of forming said teeth.

In accordance with a preferred embodiment of my invention, I provide rolled gear teeth in which the rain of the metal follows the contour o the teeth, while the metal is compacted to provide teeth of extreme density, strength, durability, and refinement of grain.- Furthermore, owing to the fact that the grain of the metal of each tooth is in pyramidal or trussed form, the teeth offer a high resistance to bending or shearing stresses.

In manufacturing the gear teeth of a gear wheel in accordance with my invention I form the toothed periphery of the gear wheel by rolling a blank in a. heated state against a toothed die member and concurrently causing a relative movement of approach between the die member and the blank. Dur ing. the entire tooth rolling, operation I maintain synchronous relations between the teeth on the die member and the teeth on the blank, so that the teeth of the die will enter the blank in a radial path from the time the tooth forming operation begins until it is ended. I prefer to maintain the aforesaid synchronous relations between the teeth of the die member and the teeth of the blank by driving the toothed die member and the blank at a fixed speed ratio so that the lineal velocity of the imaginary line on the blank, which, when it has become a finished gear will be known as its pitch line, will be equal to the pitch line velocity of the toothed die member from the time the operation of forming the teeth is begun until it is completed.

As each tooth is rolled the metal is of the metal in the teeth but also refines the grain, thereby increasing the strength of the teeth and producing a better surface condition for wear. Furthermore, owing to the fact that the teeth of thedie member enter the blank in a radial path the fiber or grain of the metal of the blank is not cut during the rolling operation but follows the serrated contour of the gear, so that the grain of the metal of the finished gear has a trussed or pyramidal form.

Metallurgy and metallography, though ancient sciences, are undergoing rapid development, and new discoveries pertaining to them are constantly being made. In the light of the present knowledge on the subject, however, I will now explain what be lieve to be the effect of the die on the metal of the blank.

It is said, and is probably true, that the more metal is worked the more homogeneous and refined it becomes. Therefore, however well the metal of the blank may have been previously worked, it is still further refined by the kneading action of ithe die,

and this refining is effected under the most favorable conditions. That is, the volume of metal acted upon, a. volume no greater than the content of one tooth, is so small that it is affected clear through. Moreover, the volume is so small that there can be but little difl'erence between the internal and eX ternal temperature; The effect of the die on the blank is elongation of certain portions of the metal. This elongation is approximately parallel to the sides of the tooth, and any seams which may have remained after the previous treatment of the metal composing the blank are elongated and laid approximately parallel to thesides'of the tooth, and therefore perpendicular to the strain, normally imposed upon the tooth. Moreover, if the heat is suflicient there is more or less elimination of these seams by their sides becoming welded.

The refinement of the metal consists mainly in breaking up the crystals, mixing them more intimately together and breaking up the cleavage planes along which they would yield. This increases the cohesion and adhesion of the crystals, and hence the mechanical strength of.-the metal, and also increases its specific gravity and hardness. There is also more or less elongation of the crystals in the direction of the elongation of the metal, which, by making the transverse cleavage planes short relative to the logitudinal cleavage planes, increases the tensile strength of the metal in the direction of its elongation. The elongation of the metal is in a general way radial to the axis of the blank and therefore, as above stated, approximately parallel to the sides of the teeth. The normal strain, that is, the workin pressure, on the teeth is against their sic es, which places the metal of one side in tension and that of the other side in compression. This tension and compression is therefore in the direction in which the tensile strength of the metal has been strengthened by elongation of the crystals. Microscopic examination of portions of a gear made by my process from a normal drop forging discloses the fact that while in the metal not affected by the die the pearlite is gathered together in rather large islands, in the matrix of ferrite, in the metal which has been acted upon by the die the islands of pearlite are small, well broken up and very uniformly distributed. The elongation of the crystals referred to is also quite apparent. I

From the foregoing it is manifest that the crystalline and fibrous structure are arranged in a sort of parallelism or correlation.

forged blanks direct from the hammer, without any machine work having been done on them. They may also be crucible steel castings. These blanks are about the same outside diameter as the pitch diameter of the gears to be made from them, and as the rolling operation displaces the metal and causes it to flow outward to form the parts of the teeth outside of the pitch-line; there is prac tically no waste of metal, only a slight surplus being required to insure that the spaces between the teeth of the die member shall be entirely filled by the metal of the blank at the end of the rolling operation, and as a result the density, and therefore the strength of the gear at all points is very uniform.-

The finished gear is suitable for most industrial purposes without further treatment after the rolling operation, but where extreme accuracy is desired, or any slight irregularity exists, the gear may be finished or ground in any suitable manner, such as by running it mesh with.

another gear, and if desired, by applying an abrasive mixture for a few minutes.

In manufacturing gears by my process the blank is'heated to a high temperature I preferably form the gears from drop.

little or no probability that they will become distorted, as cut gears so often do..

By using a blank of fairly high carbon steel, the chilling effect from its contact with the comparatively cool die member during the rolling operation gives the gear 1 a hardened surface condition without any additional hardening or treating operation.

The process of manufacturing gear wheels in accordance with my invention makes it possible to employ high manganese steel for gear wheels, which metal cannot be machined into a gear commercially at the present time.

I prefer to carry out my process with machines of the kinddescribed in my pending U. S. application, Serial No. 643010 in which means are provided to maintain the peripheralpitch line velocity of the blank equal to that of the die.

I will now proceed to describe my invention with reference to the accompanying drawings, in Which- Figure 1 is a plan of a machine for rolling gear wheels in Which,the die member consists of a rack. Fig. 2 is an end elevation of said machine, Fig. 3 is a section along the line A A of Fig. 1.. Fig is a plan of a nrachine having a circular die member. Figs. 5 and 6 are diagrams illustrating the tooth forming operation.

The machines shown in the drawings are fully described and illustrated in my aforesaid co-pending U. S. application, Serial No. 6+3,010, filed August'8, 1911.

Referring to Figs, 1, 2-,and 3, the blank 'reciprocated by the pitman 7 and fly wheel 8 driven by any suitable driving means. Mounted on tlns carriage 6 are two racks 9, 10, which can be moved transversely relative to the driving rack 57 by links 11 controlled by a lever 12 as shown, so that the breakin -down die rack 9 and the finishing die rack 10 can operate upon the blank 1 in turn. A relative movement of approach between the die racks and the blank during the rolling operation is effected by rotating the hand wheel 13, thereby moving the die rack support 14.11pwardly be means of the worms 15, worm wheels 16 and screw spindles 17.

' In operation, the reciprocating movement of the carriage 6 is imparted tothe drivingrack 5 and. the die racks Qand 10. The gear 4 meshing with, is rotated by, the rack'5',' thereof the same diameter as the pitch circle of the shaft arid is enmeshed with a gear 29; f rigidly secured to shaft 19. The axis of the pivot 26is in line with the point where.- the pitch circles of gears 28 and 29 touch,

and also in line with one eclge of, gear 28.

by rotating the shaft and blank 1. By

operating the lever 12 either the breakingdown rack or the finishing rack is brought into operation, and the teeth thereof are caused to sink increasingly deeper into the blank by suitably operating the hand wheel 13 which controls the lifting of the rack support 14. Since the gear 4 and the blank rotate as a unit a circle drawn on the blank of the gear 4 would necessarily have the same lineal velocity as the said pitch circle from start to finish of the tooth forming operation; therefore, since the depth of enmeshmentof the gear and rack 5 is constant, and the die racks cannot move longitudinally relative to the rack 5, it is clear that the lineal velocity of the blank is equal to that of the racks and therefore to that of their pitch lines.

Referring to the machine shown in Fig. -'l,' shafts 18 and 19 are rotatably mounted in bearings carried by a, bed plate 20, each shaft having rigidly secured thereto a gear 21 which are connected together by an inter- 'mediate'gear 22. Shaft 18 carries a toothed breaking-down die roller 23, and shaft 19 carries a toothed finished roller 24. A plate I 25 lies upon the bed plate 20 and is pivotally secured thereto at 26. A shaft is journaled in'a bearing carried by plate-25, and on one end thereof a blank holder 2? is mounted. A gear 28 is rigidly secured to the other end Obviously, the plate 25 can be swung on the pivot 26 without varying the distance b'etween, the axis of gear 28 and the axis of the pivot 26; therefore, the depth'ofenmeshment of. gears'QS and 2-9 at the side lying upon the axis of the 'i'vot does not vary when the plate 25 :moves, from which it follows that-I the spee dl ratio between the blank and the finishing roller is fixed whether the blank is em'ifieshedwith it, with the breaking-down roller, or is anywhere between these extremes. Furthermore, since the shafts 1S 1-9 are geared together, the speed ratio between the blank finishing roller. From what has already been said, it is obvious that the lineal velocity of the pitch line of the blank is the same as that of the roller during the entire tooth forming operation. v

The action of the teeth of the die member upon the metal of the blank will now be explained in detail, with reference to Figs. 5 and 6. The position of a tooth of the die member relative to the blank at the com mencement of the tooth forming operation is illustrated in full lines in Fig. 5, and the arrow 34: a line which if extended upwardly w o'uld pass through the center of the die member (assuming it is in this case eircular). Once during each revolution of the die member this arrow pomts directly at the (5811 l3G1' 36 of the blank. If, as the tooth is caused to sink deeper and deeper into the metal of the blank, a succession of dots 37 could be made on the blank, each dot being made opposite the point where the line 34 crosses he end of the tooth and when the arrow points at the center 36, a line drawn through these dots would be straight and radial to the center of the blank. The foregoing would be equally true were the die member a rack; in that case the line 34: would be perpendicular to the pitch-line of the rack. That the tooth of the die member does enter the blank alongthis radial path 'is due to the synchronous relations maintained between the die members and the blank; 2', 6., to the fact that the pitch line velocities of the die member and blank are equal. As the tooth enters the metal of the blank it gradually displaces the'metal without cutting the grain, so that at the end of the tooth-forming operation the fiber of the metal in the tooth and at the bottom of the tooth will have taken substantially the form indicated in Fig. 6.

Fig. 6 shows a segment of a toothed gear made in accordance with the invention, the fine irregular lines illustrating the manner in which the grain of the metal follows the contour of the teeth, and the stippled portion of the surface indicating the increased density of the metal due to the process of forming the teeth. It will be realized from this that by means of my improved process, the grain of the metal is worked into a trussed or pyramidal formation, the metal of the teeth being also compacted to give a denser and more refined grain. Importance, is attached to the teeth of.- the die member tatably mounted with their axes parallel and their surfaces touching. If one of the cylinders be rotated, adhesion of its surface to the surface of the other cylinder will make that rotate also. Assuming there is no slipping the surfaces of the cylinders will evidently move through the same distance in a given time. This surface speed has been referred to above as lineal velocity. Now let the surfaces of the cylindersrepresent pitch-circles on mating gears and the problem is to provide teeth of such shape as will keep the relative motion of the gears the same as that of the cylinders rotating in contact without slip-ping. In other words the teeth must coact in such manner that the lineal velocity of the pitch-circles will be equal at 'all times.

; By the application of geometry it can be shown that by rolling together two circles, or a circle and a line, without slipping, a point which is fixed with reference to one of the circles will inscribe a line having a form and position with reference to the other circle which is conjugate to the path traversed by the point. Development of this principle has demonstrated that if a wheel having a projection at one point on. its periphery be rolled against a second wheel, of plastic material, a depression will be formed in the second wheel which is conjugate to the projec'tion. From this it. is evident that a toothed gear wheel rolled against the periphery of a. wheel of plastic material will form a succession of depressions whose sides are conjugate to the teeth of the gear, and, obviously, the projections between the spaces thus formed will have the form of gear. teeth. This method of forming gear teeth is known generating and is distinguished from other methods in that the teeth are formed by virtue of the principle of operation of the machine instead of being simply copies of previously formed templets. In other words the forming tooth is given such a motion relative to the blank as will cause it to correctly shape the teeth on the blank, though the shape of the forming tooth is not that of the spaces formed in the blank. Reverting to the requirements of toothed gears it is clear that. if proper relative motion be imparted to the blank and tooth forming gear, that is, if the circle which will eventually be the pitch circle of the blank be given such movement relative to the pitch circle-of the gear as the surface of one cylinder would have with reference Obviously, if the teeth genera-ted are to have a form which will produce equal pitch line velocity when two of them are rotated together, equal pitch line vel ocity must be maintained while the teeth are being gen erated. In U13; ed States Paten li 1,001,799, issued to me August Q9, 15911, I described and claimed a machine for rolling (generating) gear teeth while-this blank and die-roll were driven at substantiallyl equal velocities,the velocities being near though equal for practical purposes. In my copending application, Serial Number 143,010 above referred to, I have described. and claimed machines in which the velocity. ratio is quite fixed. By the use of either o'tthese machines, therefore, I can generate' gear teeth having the correct contour.

Mention has been made above of thrl: surface condition of teeth formed bymy lprocess: Not only is the metal dense, but the surfaces of the teeth are practically free from the oXid, commonly called scale, always found on forgings. This condition is very desirable because it obviates the necessity of grinding or otherwise treating the teetltl to remove scale, and it facilitates penetrat ion of the carbon in case hardening. The die teeth have a percutient as well as a comprcssive effect on the metal of the blank, which is very beneficial both to the tOzilth surfaces'and structure. The effect is anqllogous to that of the hammer in ordinary folrging operations. The teeth are in fact forged. A further advantage resides in the fact that the teeth of the dies remain in contact with the hot blank so short a time that they absorb very little heattoo little to'injure them. Moreover, the length of time the teeth are out of contact with the hot'metal is so great compared .with the length of time it is in contact ,that ample opportunity is afforded for the teeth to cool. As there is practically no limit to the number of teeth the die may have; 0., the rack may be as long, or the rotary die as large in diameter, as is necessary to keep them cool, it is clear that conservation of the die is not a problem.

It will be obvious to those skilled in the art that changes may be made without departing from the scope of my claims.

lVhat I claim is:

1. As an article of manufacture; a gear whose body is composed of metal having a given strength and whose teeth are composed of metal of increased strength.

2. As'an article of manufacture a gear whose body *is composed of metal of given refinement, and whose teeth are -composed.

; of metal of super-refinement.

metal of increased density.

4. As an article of manufacture, a gear whose body is composed of metal of given jected to heat treatment.

density and whose teeth are composed of metal ofincreased density, the metal in said gear being substantially free from stresses which would tend to distort the gear if sub- 5. Am an article of manufacture, a gear having teethin which the metallic crystals are elongated and lie in approximate parallelism to the working faces of the teeth.

6. As an article of manufacture, a gear in which the metallic crystals are elongated and wherein said crystals and the fibers of the metal in the teeth lie in approximate parallelism to the working faces of the ear in teeth,

7. As an article ofmanufacture a whose teeth the crystals are more bro on up and in which there is greater adhesion and cohesion of the crystals than in the metal composing the body of the gear, and in 1? which the fibrous and crystalline elements of the metal are so correlated as to afford the greatest mechanical resistance to strains in i the direction of the norms. working pressure on the teeth.

8. As an article of manufacture, a gear wherein the cleavage planes along which the metallic crystals would separate under strain are relatively long in the direction perpendicular to the normal strain on the teeth.

9. As an article of manufacture, a gear in V which the metal composing the teeth is more dense than the metal inthe body and wherein the fibrous structure of the teeth has a form a proximately like that of the teeth.

10. s an article of manufacture, a gear wherein the carbon content is the same in the body as in the teeth, but wherein the metal composing the teeth is harder and stronger than the metal in the body of the ear. g 11. As an article of manufacture, a forged gear wherein the carbon content is the same in the body as in the teeth, but wherein the metal composing the teeth is harder and stronger than the metal in the body of the ear. g 12. As an article of manufacture, a gear having forged teeth possessing the compact, homogeneous and refined structure characteristic of, good forgings, whose surfaces are substantially free from forging scale and from the pits andother irregularities found on the surfaces of forgings when the scale is removed.

'13. As an article of manufacture, a gear composed of mechanically refined metal, the

metal in the teeth being super-mechanically- I refined.

1%. As an artlcle of manufacture, a gear having teeth constructed on an imaginary pitch cylinder, the body of said gear being composed of metal of given density and whose teeth are composed of metal of increased density, the metal in said gear being substantially free from stresses which would tend to distort the gear if subjected to heat treatment.

15. As an article of manufacture, a gear having teeth constructed on an imaginary pitch cylinder, whose body is composed of metal having a given strength and whose teeth are composed of metal of increased strength.

16. As an article of manufacture, a gear having teeth constructed on an imaginary pitch-cylinder, the metal composing the body of the gear being of given density while the metal in the teeth is of increased density.

17 As an article of manufacture, a gear having teeth constructed on an imaginary pltch cylinder, composed of metal of given refinement while the teeth are composed of metal of super-refinement. a

18. As an article of manufacture, a gear having teeth constructed on an imaginary pitch-cylinder, the metal in the teeth being more refined than the .metal in the body, f

inary pitch-cylinder, the metal in the teeth being more refined than the metal in. the body of the gear.

i In testimony whereof I aflix my signature in the presence of two. subscribing witnesses.

HAROLD N. ANDERSON.

Witnesses:

WM. BOHLEBER, F. K. FAssn'rr. 

